It corresponds to the recursion relation of the \(\lbrace 6j\rbrace \) -symbol involving a shift of a spin label by one [1]}:
\(A_{+1}(j_1)\left\lbrace  \begin{array}{ccc}j_1+1 & j_2 & j_3 \\ j_4 & j_5 & j_6\end{array} \right\rbrace  +A_0^{(1)}(j_1)\left\lbrace  \begin{array}{ccc}j_1 & j_2 & j_3 \\ j_4 & j_5 & j_6\end{array} \right\rbrace  +A_{-1}(j_1)\left\lbrace  \begin{array}{ccc}j_1+1 & j_2 & j_3 \\ j_4 & j_5 & j_6\end{array} \right\rbrace  =0\,,\) 
